In recent years, primarily in multicarrier transmission systems, a method has been proposed in which scheduling of users is performed by dividing into multiple blocks in frequency and time domains. Here, the regions which are defined in frequency and time domains and are secured when users perform communications are called allocated slots, and the blocks that form the basis when determining the allocated slots are called chunks.
Amongst these, a method has been proposed that, when transmitting broadcast/multicast channels or control channels, blocks which are wide in the frequency direction are allocated to obtain a frequency diversity effect, which ensures few errors even with low receiving power, and when transmitting unicast signals that involve one-on-one communication between a wireless transmitter and a wireless receiver, blocks which are narrow in the frequency direction are allocated to obtain a multi-user diversity effect (for example, refer to non-patent document 1 and non-patent document 2).
FIG. 31 and FIG. 32 show the relationship between time (vertical axis) and frequency (horizontal axis) in signals transmitted from a wireless transmitter to a wireless receiver. In FIG. 31, the vertical axis represents time, and the horizontal axis represents frequency. In the time domain, five transmission times t1 to t5 are established. Each transmission time t1 to t5 has the same time width. In the frequency domain, four transmission frequencies f1 to f4 are established. Each transmission frequency f1 to f4 has the same frequency width Fc. In this manner, the transmission times t1 to t5 and the transmission frequencies f1 to f4 establish 20 chunks K1 to K20 as shown in FIG. 31.
In addition, as shown in FIG. 32, four chunks K1 to K4 are combined in the frequency direction, and divided into three in the time domain direction to establish allocated slots S1 to S3 each having a time width of t1/3 and a frequency width of 4f1. Allocated slot S1 is allocated to a first user, allocated slot S2 is allocated to a second user, and allocated slot S3 is allocated to a third user. Accordingly, the first to third users are able to obtain a frequency diversity effect.
Next, chunk K5 is allocated to a fourth user as allocated slot S4. Chunks K6 and K7 are combined and allocated to a fifth user as allocated slot S5. Chunk K8 is allocated to a sixth user as allocated slot S6. Accordingly, the fourth to sixth users are able to obtain a multi-user diversity effect.
Next, chunks K9 and K11 are allocated to a seventh user as allocated slot S7. Chunks K10 and K12 are combined, and divided into three in the time domain direction, to establish communication slots S8 to S10 each having a time width of t3/3 and a frequency width of 2f2. Allocated slot S8 is allocated to an eighth user, allocated slot S9 is allocated to a ninth user, and allocated slot S10 is allocated to a tenth user. Accordingly, the seventh to tenth users are able to obtain a frequency diversity effect.
Next, chunk K13 is allocated to an eleventh user as allocated slot S11. Chunk K14 is allocated to a twelfth user as allocated slot S12. Chunks K15 and K16 are combined and allocated to a thirteenth user as allocated slot S13. Accordingly, the eleventh to thirteenth users are able to obtain a multi-user diversity effect.
Next, chunks K17 and K19 are allocated to a fourteenth user as allocated slot S14. Chunks K18 and K20 are combined, and divided into three in the time domain direction, to establish allocated slots S15 to S17 each having a time width of t5/3 and a frequency width of 2f2. Allocated slot S15 is allocated to a fifteenth user, allocated slot S16 is allocated to a sixteenth user, and allocated slot S17 is allocated to a seventeenth user. Accordingly, the fourteenth to seventeenth users are able to obtain a frequency diversity effect.
[Non-patent document 1] “Downlink Multiple Access Scheme for Evolved UTRA”, Apr. 4, 2005, R1-050249, 3GPP.
[Non-patent document 2] “Physical Channel and Multiplexing in Evolved UTRA Downlink”, Jun. 20, 2005, R1-050590, 3GPP.